1. Field of the Invention
The present invention relates to blood collection sets for safe and convenient handling of needles. More particularly, the present invention relates to a blood collection set including a needle assembly having a forward moving safety shield for protection from a used needle tip.
2. Description of Related Art
Disposable medical devices having piercing elements are typically used for administering a medication or withdrawing a fluid, such as blood collecting needles, fluid handling needles and assemblies thereof. Current medical practice requires that the fluid containers and needle assemblies used in such systems be inexpensive and readily disposable. Consequently, existing blood collection systems, for example, typically employ some form of durable, reusable holder on which detachable and disposable needles and fluid collection tubes may be mounted. A blood collection system of this nature can be assembled prior to use and then disassembled after usage. Thus, these blood collection systems allow repeated use of the relatively expensive holder upon replacement of the relatively inexpensive needle and/or fluid collection tube. In addition to reducing the cost of collecting blood specimens, these blood collection systems also help minimize the production of hazardous medical waste.
A blood collection set or intravenous (IV) infusion set typically includes a needle cannula having a proximal end, a pointed distal end and a lumen extending therebetween. The proximal end of the needle cannula is securely mounted in a plastic hub with a central passage that communicates with the lumen through the needle cannula. A thin flexible thermoplastic tube is connected to the hub and communicates with the lumen of the needle cannula. The end of the plastic tube remote from the needle cannula may include a fixture for connecting the needle cannula to a blood collection tube or some other receptacle. The specific construction of the fixture will depend upon the characteristics of the receptacle to which the fixture will be connected.
In order to reduce the risk of incurring an accidental needle-stick wound, protection of used needle tips becomes important. With concern about infection and transmission of diseases, methods and devices to enclose the used disposable needle have become very important and in great demand. For example, some needle assemblies commonly employ a safety shield that can be moved into shielding engagement with a used needle cannula without risking an accidental needle stick.
U.S. Pat. Nos. 5,085,639, 5,088,982 and 5,154,699 disclose safety winged needle devices for use with blood collection sets or infusion sets. The safety needle devices of these patents include an inner tube and an outer tube having cooperating surfaces in contact with each other, with the cooperating surfaces having mating grooves and ramps. By applying a force in opposing directions on the inner and outer tubes, the outer tube is forcibly moved along the ramps and into engagement with the grooves of the inner tube, thereby moving the outer tube, and therefore the outer shield, into a shielding position and locking the shield in place about the needle tip. The cooperating surfaces of such outer and inner tubes, however, provide a frictional engagement which requires much force to overcome. Moreover, maintaining an appropriate grip on the needle device to forcibly move the outer and inner tubes apart can be difficult due to the profile of the needle device.
U.S. Pat. No. 6,165,157 discloses a needle guard which includes a “thumb-knob” or protrusion on the outer guard to assist in manipulation of the outer guard by providing an abutment against which the thumb of the user can push in order to pull the needle and needle mount into the outer guard using only one hand. Retraction of the needle in this manner, however, requires the user to grip the flexible tube in the user's palm, which does not provide an effective gripping surface for maintaining the needle device in place during retraction, and may cause the flexible tube to be separated from the needle device during retraction.
Accordingly, a need exists for a needle assembly for use with a blood collection set which achieves secure and effective shielding of a used needle tip and which is simple and inexpensive to manufacture and easy to operate.